Phase Transition in Gauge Theories and the Planck Scale Physics

The present paper is based on the modified part of the review "Random Dynamics and Multiple Point Model" by L.V.Laperashvili, H.B.Nielsen, D.A.Ryzhikh and N.Stillits, in preparation for publication in Russian, which contains the results of our joint activity with H.B.Nielsen concerning the investigations of phase transitions in gauge theories. In this review we have presented the main ideas of the Nielsen's Random Dynamics (RD) and his achievements (with co-authors) in the Anti-Grand Unification Theory (AGUT) and Multiple Point Model (MPM). We have considered also the theory of Scale Relativity (SR) by L.Nottale, which has a lot in common with RD: both theories lead to the discreteness of our space-time, giving rise to the new description of physics at very small distances. In this paper we have demonstrated the possibility of [SU(5)]$^3$ SUSY unification with superparticles of masses $M\approx 10^{18.3}$ GeV and calculated its critical point -- critical value of the inverse finestucture constant -- at $\alpha_{5,crit}^{-1} = \alpha_5^{-1}(\mu_{Pl})\approx 34.0$ (close to $\alpha_{GUT}^{-1}\approx 34.4$) with a hope that such an unified theory approaches the (multi)critical point at the Planck scale.